Phosphatic fertilizer



Patented Apr. 25, 1939 UNITED STATES PATENT OFFICE PHO SPHATIOFERTILIZER Friedrich P. Kerschbau assignor to Harold D.

No Drawing.

Serial No. 103,458. 1935 The invention relates to the production ofphosphatic fertilizers and particularly to the production of fertilizersby the conversion of the phosphoric acid content of mineral phosphatesinto 5 available form.

A principal purp duction of phos phosphates.

A further purpose of the invention is to provide a process whereby thephosphoric oxide content of mineral phosphates may be made available forfertilizer purposes without the use of acid treating agents.

It has been found th of proportions and bring about a re'actio orthotites, phos Claims.

ose of the invention is the prophatic fertilizers from mineral at bya'suitable choice onditions it is possible to 11 between tri-alkalimetal phosphates and mineral phosphates, apasuch as Florida pebblephosphates, Morocco phates or flotation concentrates, wherebysubstantially the entire phosphorous content of the materials isconverted into ammonium citrate-soluble form.

Instead of a tri-alkali metal phosphate, such as N33P04 or K3PO4,substances capable of forming such phosphates under the conditions ofthe process may be used, for example, mixtures of alkali metal metaorpyro-phosphates, or monoor di-alkali metal ortho-phosphates, with thecorresponding proportion of alkali metal hydroxide or carbonate to givethe tri-alkali metal ortho phosphate. Such substances are thereforesubstantial equivalents of tri-alkali metal phosphate in the method ofthe invention.

It has been found that to obtain a satisfactory conversion of thephosphatic material to a product of high content of ammonium citratesoluble phosphorus, it is necessary to treat the mineral phosphate withthe tri-alkali ortho-phosphate, or

its equivalent, in the amount of at least 0.5 mole, and preferably about0.8 mole, of P205 as trialkali ortho-phosphate to every mole of P205 inthe mineral phosphate and it is preferable to carry out the treatment ata temperature not substantially exceeding about 1200 C.

It has further been found that the conversion of the mineral phosphateinto available form is greatly promoted by the presence of alkali metalchlorides, such as sodium and potassium chlorides .or any alkali metalsalt of an anion that does not chemically react with the mineralphosphate, such as alkali metal nitrate. In the presence of thesepromoting agents a substantially quantitative conversion of the mineralphosphate into am-, monium citrate-soluble form may be effected at atemperatures as low as 800 C., or even lower,

m, Winter Haven, Fla.,

T. Stowell, Washington,

Application September 30, 1936,

In Austria October 7,

while in the absence of such promoters a temperature of about 1000 to1100 C. is preferable. vThe promoting agent is advantageously used in anamount of at least one mole, preferably two to three moles or more, permole of tri-alkali 5 metal phosphate or its equivalent.

The following examples are illustrative embodiments of the principles ofthe invention:

1. Fifty kilograms of calcined Florida pebble phosphate containing36.55% P205 was mixed 10 with thirty-eight kilograms of technicaltrisodium phosphate containing 38.26% P205. The mixture was heated to atemperature of about 1000 C. for about l /z hours. The product contained38.55% P205 of which 99.0% was amlit monium citrate soluble and 99.4%citric acid soluble. The pH of the product was 10.5.

2. The trisodium phosphate of Example 1 Was replaced by an equivalentamount of an equimolecular mixture of sodium metaphosphate and sodiumcarbonate. In this case also 99% of the P205 content of the product wasammonium citrate soluble.

3. Fifty kilograms of the calcined Florida pebble phosphate used inExample 1 was mixed with thirty-eight kilograms of technical trisodiumphosphate and fifty kilograms of potassium chloride. The mixture washeated to a temperature of 800 to 850 C. for about 1 hours. The prodnotcontained 23.5% K20 and 24.5% P205, of which 11.1% was water-soluble,94.7% was ammonium citrate soluble, and 95.6% citric acid soluble. ThepH of the product was 11.3.

The conversion process may be advantageously effected in a rotary kiln,although other appara- 5 tus, for example, a shaft furnace may also beused. It is sometimes advantageous, for example, when operating in ashaft furnace, to form the mixture of materials into agglomerates beforecharging into th furnace. A particularly advantageous metho of operatingthe process is to bring about the reaction on a traveling palletmachine, of the type of the well-known Dwight- Lloyd sintering machine,in which case all or a part of the fuel necessary to provide the neces-4 sary temperature may, if desired. be added to the charge on themachine.

The phosphatic rawmaterial may be advantageously pretreated or enrichedby treating it, -for example, with the residual gases from a phosphorusblast furnace or other gases containing residual amounts of phosphorus,phosphorus pentoxide or phosphoric acid, or even with the weakphosphoric acid containing water from a phosphorus condensing operation.In this way 56 it is irequently possible to increase the P205 contentoiv phosphatic raw materials by as much as 20%, The amount oi tri-alkalimetal phosphate used for the conversion of such enriched phosphaticmaterials may be reduced with advantage to as low as 0.5 mole(equivalent P305) to each mole of R05 in the treated phosphaticmaterial.

it will he apparent from the foregoing description that the inventionprovides a simple and economical method for the conversion oi phosphaticmaterials into highly valuable basic fertilizers and particularly mixediertilizers which may contain, in addition to P205, K20, Nam, 32.0, andother desirable components.

it will further be apparent that the invention is not limited to theillustrative examples and that the conditions o1! operation, iorexample, the temperature under which the most effective conversion oithe most economical results are obtained, vrlll vary the otherconditions, such as the relative proportions of the materials, thecharacter oi the phosphatic raw material, the time of heating and thelike,

I claim:

1, Process for the production of phosphatic materials suitable forfertilizers, comprising heating a mixture of a mineral phosphate and atrialkali metal orthophosphate, in the proportion of at least 0.8 moleof P205 in the alkali metal phosphate to each mole of P305 in themineral phosphate, to a temperature oi from about 1000 to about 1200" C.

2. Erocess tor the production of phosphatic materials suitable forfertilizers, comprising heating a mixture of a mineral phosphate and atrialkali metal orthophosphate, in the proportion of at least 0.8 moleof PzOs in the alkali metal phosphate to each mole of P205 in themineral phosphate, to a temperature of from about 800 to about 1200 C.,in the presence of at least one mole of a conversion-promoting agent 01the group consisting of the alkali metal chlorides to arouses each moleof trialkali metal ph or its equivalent.

3. Process for the production of phosphatlc materials suitable forfertilizers, comprising; heat: ing a mixture of a mineral phosphate anda trialkali metal orthophosphate, in the proportion of at least 0.8 moleof P205 in the alkali metal phosphate to each mole of P205 in themineral phosphate, to a temperature oi from about 800 to about l000 0.,in the presence of at least one mole of a conversion-promoting agent ofthe group consisting oi the alkali metal chlorides to each mole oftrialkali metal phosphate or its equivalent.

i. A process for the production of phosphate materials suitable forfertilizers, comprising heating a mixture of a mineral phosphate, whichhas been treated with a substance of the group consisting of phosphoruspentoxide and phosphoric acid to increase the P205 content of thephosphate, and a trialkali metal phosphate, in the proportion of atleast 0.8 mole of P205 in the alkali metal phosphate to each mole ofP205 in the original mineral phosphate, to a temperature of from about1000" C. to about 1200 C.

5. A process for the production of phosphate materials suitable forfertilizers, comprising heating a mixture of a mineral phosphate, whichhas been treated with a substance of the group consisting of phosphoruspentoxide and phosphoric acid to increase the P205 content or thephosphate, and a trialkali metal phosphate, in the proportion of atleast 0.8 mole of P205 in the alkali metal phosphate to each mole ofP205 in the original mineral phosphate, to a temperature.

of from about 800 C. to about 1200" C. in'the presence of at least onemole of a conversionpromoting agent of the group consisting of alkalimetal chlorides to each mole oi trialkall phosphate or its equivalent.

FRIEDRICH P. KEBSCHBAUM.

